Solar updraft towers (also known as solar chimneys) are a simple and reliable way to generate electricity using solar radiation and the principle of convection. Referring to FIG. 1, an example of a prior art solar updraft tower is shown. Such solar updraft towers may comprise: a base 20; collectors 10; and a tower 5. The collectors may comprise a greenhouse covering 12, and a heating space 14, which is formed between the greenhouse covering and the ground. The base may comprise heated air inlets 22, and turbines 26. Sunlight 1, passes through the greenhouse covering and heats up the air in the heating space. The heated air then flows through the air inlets into the base and up through the tower to reach the cooler mass of air located above the tower. This convection flow of heated air drives the turbines, producing electricity.
Solar updraft towers present a number of advantages. They may be constructed from relatively inexpensive and common materials and they do not require a continuous supply of water to operate. Also, because the designs typically incorporate huge thermal masses, the variability of their electrical output is very low and it is possible for them to continuously produce electricity. Finally, their designs are not maintenance-intensive; the only components that require regular maintenance are the turbines, which, in many designs, are located at ground level. These significant advantages notwithstanding, there are also shortcomings associated with the design of solar updraft towers. They require very tall, freestanding chimney structures to deliver heated air from the collectors up to cool masses of air located high above ground level.
Current solar updraft tower designs incorporate chimney structures constructed using traditional materials, such as steel. A taller chimney structure increases the efficiency of the solar updraft tower, but obviously also increases the cost of construction as well. Furthermore, as designs incorporating chimney structures 1,000 meters or taller have been proposed, the design of chimney structures presents a substantial engineering challenge. Finally, the potential for damage arising from the collapse of chimney structures constructed using traditional materials is high.
Another important shortcoming of the prior art solar updraft tower design is very low efficiency. Only between 0.5% and 5% of the incident solar energy is converted into electricity.
It is therefore desirable to provide a self-supporting chimney apparatus that overcomes the shortcomings of prior art chimney structures.